Invasive species of plants are infesting native areas and crowding out native plants. Among the most destructive are purple loosestrife and phragmites. Since these invasive plants have no natural enemies, they eventually take over large areas where they are unwanted.
Spraying with a herbicide is an unacceptable method of control unless 90% or more of the growth is desired to be eliminated, as spraying is non-selective and will kill all plants contacted. Selective cutting of certain species of invasive plants may restrain their growth for a time, however the control agent of choice is systemic postemergent herbicides. Systemic postemergent herbicides are drawn into the tissues of a plant, disrupting its natural function and destroying it from within. Such herbicides are commonly used on herbaceous perennial weeds or woody weeds such as the aforementioned purple loosetrife.
Systemic herbicides, however, are extremely virulent. Many postemergent herbicides are so toxic that even a small amount will kill any plant tissue it touches. Such herbicides must not be used near vegetable gardens, drainage fields, wetlands, streams or garden pools. Such chemicals can wash onto other plants, kill fish, and pollute water supplies, and can harm a tree or shrub if drawn into its roots.
Many systemic herbicides are so dangerous to use that, during an application, users are recommended to avoid drinking, smoking, eating, or touching the face. Pets and children must be removed from any area where such chemicals are to be used.
I participated in a project to remove a growth of purple loosestrife. Immediately after each plant was cut, a drop of a systemic herbicide was applied to the wound with an eye dropper. The effectiveness in killing the invasive was determined to be between 50% and 100%, depending on the thoroughness in applying the herbicide to the plant wounds. In heavy brush we found it to be difficult to locate the stumps of the just-cut plant stems and branches.
While the herbicide was determined to be effective in killing the undesired plant, the time and effort required was completely unacceptable.
A common method of applying a systemic herbicide to an individual plant is to surround the plant to be killed with scrap paper. Wearing gloves, the wounds of the cut plant are brushed with a herbicide. Care must be taken not to drip any of the chemical on the surrounding area, and not to touch any plant with the soiled paper.
Users are advised, after a systemic herbiciding operation, to wash all clothing and to shower. It is recommended that such potent herbicides be stored under lock and key.
Neither of the described methods is practical for controlling invasives forming borders, hedges, ground covers or other dense twiggy masses containing large numbers of plants, or less dense woody invasives covering large areas.
U.S. Pat. Nos. 2,870,573 (Scadden); 4,783,907 (Ravoux); 4,891,882 (Bloom et al) and 2,747,330 (Simpkins) each describe hand shears adapted for cutting a plant branch and simultaneously applying a systemic chemical to the plant wound. In each of the identified patents, the herbicide is applied to the blade or blades of the shears, rather than to the wound itself. The herbicide is transferred from the blade to the wound in successive cuts.
Such devices which indirectly apply plant treatment chemicals have a number of shortcomings. By applying the chemical to the blade surfaces, the subsequent transfer of the chemical to the plant being cut is quite ineffective, as most of the chemical is merely scraped off by the exterior surface of the branch being cut as the blades pass into the branch. Application of the chemical to the blades will cause substantial losses due to evaporation, drippage from the blades, etc. If the wasted material is a systemic herbicide, being extremely toxic, it is apt to come in contact with and possibly kill native plants and other plants desired to be protected. Drippage of such a herbicide from the blades is a serious safety threat to the user as he or she moves through the area being treated, as well as to pets and children which may frequent the treated area at the time of, or shortly after, the herbiciding operation.
Further, the shears are contaminated against use for other purposes by the inundation of the blades with a plant treatment chemical. In addition, the use of hand shears, cutting one branch at a time, is much too slow for a large area application such as a large bed of purple loosestrife or other invasives.
U.S. Pat. Nos. 773,743 (Von Hoffmann); 1,056,046 (Myers) and 5,088,198 (Drusiani) disclose hand shears in which a plant control chemical is sprayed on the plant branch wound as the branch is cut.
This class of chemical-applying hand shears suffers from many of the limitations of the afore-discussed hand shears which apply the chemical indirectly. The class of devices utilizing a chemical sprayer are more threatening to the surrounding environment and to the user due to the difficulty in controlling the spray. Wasteage is a serious problem also.
U.S. Pat. No. 4,219,963 (Mullett) depicts chemical-applying hand shears in which a plant control chemical is sprayed on the wound of the plant, independently of the cutting action. After the cut is made, the chemical dispensing nozzle is aimed at the wound and a trigger-controlled pump projects fluid in the direction in which the nozzle is aimed.
The present invention overcomes the disadvantages of the aforediscussed prior art approaches and is useful in applying systemic plant control chemicals of many types including fungicides and sterilizers as well as herbicides.